A TEM study of particles carried by ascending gas flows from the Bairendaba lead-zinc deposit, Inner Mongolia, China

Abstract

In order to find deep-seated deposit, there is a need to develop non-traditional surface geochemistry. Geogas is of particular interest. Particles transported by geogas from the deeply concealed deposits potentially hold great information. This study investigates particles carried by ascending gas flows from the Bairendaba lead-zinc deposit. This deposit is covered by a thick exotic substance, which hinders probing the ore body directly. The samples were collected using a static sampling method and were analysed by transmission electron microscopy (TEM) to observe particle features (such as shape, component, size, structure, and form of polymerization); these particles contain information on buried deposits. Numerous Pb-, Zn-, and Cu-bearing particles, as well as particles containing other metal compounds, occur as individuals or aggregates in the ascending gas flows. Most particles have a large oxygen (O) content; this is likely caused by the course of gas flows ascending from the deep ore body to the ground surface. Sulphur (S) is commonly associated with Pb, Cu, As, Fe, and Sb and occurs as sulphate in this deposit. Most metallic elements occur as sulphate, oxide, and carbonate in the detected particles. In contrast to the samples collected in the peripheral area, samples collected from the concealed deposit include numerous particles containing metallogenic elements, although particles containing major elements can be found in both areas. Moreover, the trend of each Pb- or Zn-bearing particle along a unique sampling line is directly related to the distribution of the corresponding ore bodies; this indicates that the particles were generated at a certain depth, carried by the ascending gas flow and directly provide important information regarding the concealed ore bodies. The anomalous area can be used as a basis for further prospect analysis and improve the prospecting success rate.